Discovery of New Hormone-Generating Cells Sheds Light on Monogamy in Mice

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Researchers from Columbia University's Zuckerman Institute have identified a previously unknown hormone-generating cell that may explain why the Oldfield mouse exhibits lifelong monogamy, unlike its promiscuous relatives. This study, published in Nature, focused on the differences between two closely related mouse species: the monogamous oldfield mouse and the promiscuous deer mouse.

The research revealed significant differences in the adrenal glands of these mice. The monogamous oldfield mouse has six times heavier adrenal glands than the promiscuous deer mouse. Genetic analysis showed that a gene called Akr1c18 is more active in the monogamous species. This gene encodes an enzyme that produces 20⍺-OHP, a little-studied hormone in mice and humans. Administration of 20⍺-OHP increased nurturing behaviours in the promiscuous mice, such as grooming and caring for their pups, which were previously absent.

Further investigation discovered a unique fourth zone in the adrenal glands of the monogamous mice, named the zona inaudita. This zone contains cells with high activity of 194 genes, including Akr1c18, which are not found in the adrenal glands of the promiscuous mice. This new structure appears to have evolved rapidly within the past 20,000 years.

These findings suggest that the hormone 20⍺-OHP and the newly identified adrenal cells are crucial in promoting monogamous behaviour and parental care. The study could offer new insights into parenting behaviours in humans, especially since 20⍺-OHP is related to allopregnanolone, a compound used in treating postpartum depression. The research opens the door for further studies on the link between 20⍺-OHP and human parental behaviour.